I think one of the most important things I learned during my pediatric training was the importance of a chest X-ray. I had an outstanding resident at Los Angeles Children's Hospital who said, "If you are puzzled about a diagnosis, order a chest X-ray." This has paid off so very many times.
I am constantly amazed at how even people with cancer say their doctors have never ordered a chest X-ray despite them telling the doctor they are short of breath. Too often everything is thought to be caused by the primary diagnosis.
I saw a two-year-old child one day who had been followed by another doctor. The little boy had been treated with several courses of antibiotics because he was coughing and wheezing. I ordered a chest X-ray and asked that the neck be included. It was hard to believe my eyes when I saw the X-ray. The child had a safety pin in his wind-pipe or trachea! A very skilled ear-nose and throat doctor removed it and the child recovered well with no further problems.